1. Field of the Invention
The present invention relates generally to devices and methods for setting the tape wrap angle for essentially flat contour tape recording heads, and more particularly to a device and method which utilizes a signal from the tape to provide an initial point for setting the tape wrap angle.
2. Description of the Prior Art
Magnetic tape drives operate by the passage of magnetic tape across a tape recording head which includes a plurality of tape writing elements and tape reading elements. A typical tape drive includes an actuator means for moving the tape head laterally relative to the longitudinal axis of the tape, such that the tape head reading and writing elements may access different data tracks on the magnetic tape, and a typical magnetic tape may have hundreds of data tracks written on it. A typical magnetic tape also includes a plurality of servo tracks that are written onto the tape during manufacturing, and which are used by the tape drive for tape head alignment and control purposes.
For efficient writing and reading of data to and from a magnetic tape, it is necessary that the tape make direct physical contact with the data writing elements and data reading elements of the tape head. Typical prior art tape heads have been fabricated with a convex curve contour head surface, with the write and read sensors generally centrally disposed in the curved surface. A tension force is placed upon the tape, such that it is pulled tightly enough across the curved head surface to make contact with the read and write sensors of the head. The tension force and the movement of the tape across the head surface can create significant tribological effects that can degrade the performance of magnetic tape drives having such curved tape heads and unwanted wear on the magnetic tape. Additionally, the fabrication of such curved tape heads can be relatively difficult and expensive.
In an effort to improve upon the curved surface tape heads, flat contour tape heads have been developed. Such flat contour heads are simpler and generally less expensive to fabricate. However, it can be more difficult to obtain contact between the magnetic tape and the read and write sensor elements where the tape head surface is flat. It has been found and described in the prior art, that when the magnetic tape is directed towards the planar flat surface of the tape head at a slight angle, termed the tape wrap angle, that an air pressure differential can be created, such that the magnetic tape is pressed against the flat tape head surface by the air pressure differential. When the tape wrap angle is properly selected, harmful tribological effects and magnetic tape wear are minimized, while significant data read and write functions are achieved due to the contact of the magnetic tape with the read and write elements of the flat contour tape head.
It is therefore important in such prior art flat contour tape heads that the tape wrap angle be easily and accurately set. In the prior art, the method for setting the tape wrap angle involves the utilization of precise mechanical tools and measurements, and the method for setting the tape wrap angle was therefore cumbersome and time intensive, and was not always consistently, accurately repeatable. As is described hereinbelow, the present invention is a quick, easy and therefore less expensive method for setting the tape wrap angle, which utilizes the electronic signal generated by prewritten data tracks, such as the servo tracks, of the magnetic tape to accurately determine an initial point for setting the tape wrap angle. The accurate setting of a desired tape wrap angle from the initial point is then easily accomplished.
The present invention is a method for setting the tape wrap angle for a flat, or nearly flat, contour linear tape recording head of a magnetic tape drive. At the final stages of the tape drive manufacturing process, the tape drive includes a tape read/write head, a magnetic tape within a tape cartridge and a take-up reel. Such magnetic tapes generally include a plurality of servo tracks that are provided by the manufacturer on the tape for purposes such as tape head alignment and movement control. To facilitate the setting of the tape wrap angle of such tape drives, an adjustable tape movement control device is located proximate each side of the tape head, and the tape movement control device is operable to move the tape relative to the flat planar surface of the tape head to adjust the tape wrap angle.
The present invention utilizes the effect that a precise and repeatable nominal tape wrap angle exists at which reading signals from the magnetic tape ceases and/or commences. Specifically, where the tape wrap angle is greater than the nominal value, such as 0.1xc2x0, the read signal from the magnetic tape will be strong, whereas when the tape wrap angle is less than the nominal approximately 0.1xc2x0 value the read signal from the tape ceases. Thus, the nominal tape wrap angle can be easily determined by monitoring the servo track signal, or other prewritten data track signals (or even a native tape signal), while the tape wrap angle is adjusted. When the tape read signal ceases (or starts, depending upon the direction of adjustment) an initial position of the tape movement control device relative to the tape wrap angle is identified. At this initial position it is known that the tape wrap angle is at its nominal value, such as approximately 0.1xc2x0. Thereafter, the tape movement control device can be knowingly adjusted with a calibrated indicator to accurately and quickly achieve a desired final tape wrap angle.
It is an advantage of the method for setting the tape wrap angle for an essentially flat contour tape recording head of the present invention that it utilizes an electronic signal from the magnetic tape to determine a nominal tape wrap angle which is utilizable as an initial point for setting the desired tape wrap angle.
It is another advantage of the method for setting the tape wrap angle of the present invention that the tape wrap angle can be accurately and repeatably set.
It is a further advantage of the method for setting the tape wrap angle of the present invention that the tape wrap angle can be rapidly and inexpensively set.
It is yet another advantage of the method for setting the tape wrap angle of the present invention that magnetic tape drives can be more reliably and inexpensively manufactured.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawings.